With rapid development of wireless communication technologies, spectrum resources are increasingly scarce. By monitoring and studying wireless communication spectrums, it is found that some bands (such as a television band) are not used in most of time or not used within most areas, while multi-user or multi-system competition occurs in some other bands. In other words, the use of the spectrum resources is imbalanced. CR technology emerges under this background. The basic principle of CR is described as follows. Under the premise of not disturbing an authorization system and by monitoring changes of current wireless communication environment, white space spectrums of the authorization system are accessed, in the form of the dynamic opportunistic spectrum access, for communications.
The premise of opportunistically accessing, by a CR system, the white space spectrums of the authorization system is that services of the authorization system are not disturbed by the CR system. Based on this requirement: (1) the CR system may have a capability of accurately determining the white space spectrums of the authorization system; (2) the CR system may have a spectrum handover capability, i.e., when the CR system detects that the authorization system appears on a white space spectrum currently used (i.e., a source working frequency), the CR system may promptly exit from the white space spectrum currently used. In order to ensure the business continuity of the CR system, during the spectrum handover, when the CR system exits from the source working frequency, the CR system is handed over to another white space spectrum (i.e., a target working frequency) for reestablishing services.
FIG. 1 is a schematic diagram illustrating a method for implementing the spectrum handover in the CR system. As shown in FIG. 1, a based station sends a spectrum handover command to a user equipment (UE) to notify the UE to stop data transmitting and receiving on the source working frequency and reestablish a cell on the target working frequency. When receiving the spectrum handover command, the UE leaves the source working frequency and performs downlink synchronization with the target working frequency. When the downlink synchronization with the target working frequency is completed, the UE performs a random access procedure on the target working frequency, so as to perform uplink synchronization with the base station through the random access procedure. Specifically, the UE sends a random access preamble to the base station and the base station sends a random access response to the UE. The UE sends a spectrum handover completing message to the base station and the base station sends a competition solving message to the UE. In addition, after the random access procedure is completed, the spectrum handover is completed.
During the spectrum handover procedure of the CR system, UEs in a connection state within the cell are handed over to the target working frequency. As such, all of the UEs in the connection state initiate the random access procedure on the target working frequency within a short period, which causes a serious random access conflict.
During the process of implementing various examples of the present disclosure, the inventors find that the prior art at least has disadvantages described as follows. During the spectrum handover procedure of the CR system, there is not a reasonable solution for solving the random access conflict, which results in a higher failure probability of the spectrum handover and long service interruption time. Moreover, users at different service levels could not be processed distinguishingly, so that user experience of the CR system is influenced.